The present invention relates to movable parts of compressors, and, more particularly, to parts on which lubrication coatings are applied for reducing friction.
As described in Japanese Unexamined Patent Publication Nos. 60-22080, 8-199327, and 10-205442, a piston of a swash plate type compressor reciprocates by rotation of a swash plate, which rotates integrally with a drive shaft of the compressor. More specifically, shoes connect the piston to opposite surfaces of the swash plate, thus transmitting motion of the swash plate to the piston. The shoes are formed of iron-based material and they slide on the swash plate when the swash plate rotates. This wears sliding the portion of each shoe that contacts the swash plate and the sliding portion of the swash plate that contacts the shoes. The sliding contact may also result in a seizure between the shoes and the swash plate. It is thus necessary to reduce friction between the shoes and the swash plate.
The sliding components of the compressor wear quickly or are likely to cause a seizure particularly under severe conditions, for example, when the components are not sufficiently lubricated immediately after the compressor is started or when an increased load is applied to the movable components.
Accordingly, in each aforementioned publication, each sliding portion of the swash plate that contacts the shoes is provided with a lubrication coating. The main component of the lubrication coating is molybdenum disulfide, which is a solid lubricant. The coating also contains graphite. The lubrication coating enables the swash plate to move smoothly with respect to the shoes.
However, seizure may still occur under severe conditions and various other conditions, for example, when the compressor is operated at a relatively high speed or with a relatively small displacement, which causes insufficient lubrication. Thus, to solve this problem, the amount of solid lubricant transferred to the component contacted by the coating is increased to prolong the life of the lubrication coating. The present invention focuses on this point. Further, the present invention has been accomplished based on a number of experiments.
Accordingly, it is an objective of the present invention to provide a lubrication coating that is applied to a sliding component of compressor to reduce friction.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, the invention provides a part of a compressor. The part is one of a pair of parts that slide with respect to one another. A lubrication coating is applied to the part. The lubrication coating includes a non-graphite solid lubricant, a transfer adjusting agent and a resin binder. The transfer adjusting agent adjusts the amount of the solid lubricant transferred from the part to the other part of the pair.
Graphite with a stratified or flaky crystalline structure has an improved lubrication performance, as compared to the substance in the form of particles (or fine powder). A conventional graphite-contained lubrication coating thus employs vein graphite that has a relatively high lubrication performance. In contrast, amorphous graphite has a relatively low lubrication performance and is contained in a lubrication coating that contains non-graphite, solid lubricant. However, if the compressor is operated under the aforementioned severe conditions, this lubrication coating, which contains the non-graphite solid lubricant and the amorphous graphite, indicates a higher lubrication performance than the conventional lubrication coating that contains the vein graphite. It is thus assumed the amorphous graphite promotes transfer of the non-graphite solid lubricant to the component contacted by the coating, although the lubrication performance of the substance is relatively low. In other words, the amorphous graphite functions as a transfer adjusting agent.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.